1. Field of the Invention
The present invention relates to an image displaying apparatus utilizing an electron beam such as a field emission display (FED) and a cathode-ray tube (CRT).
2. Related Background Art
So far, image displaying apparatuses such as CRT""s have always been required to have further larger screens, and research therefor is lively being performed. Moreover, as the screens become larger, it becomes an important problem to make the apparatuses thinner in thickness, lighter in weight, and lower in costs. However, because a CRT deflects electrons accelerated by a high voltage with the deflection electrode thereof to excite the phosphor on the face plate thereof, it becomes necessary to lengthen the depth thereof in principle, and then it becomes difficult to provide a CRT thin in thickness and light in weight. The present inventors have researched in respect of a surface conduction electron-emitting device and an image displaying apparatus using the surface conduction electron-emitting device as an image displaying apparatus capable of resolving such a problem.
For example, the inventors have tried to apply a multi-electron beam source by an electric wiring method shown in FIG. 11 to an image displaying apparatus. That is, the inventors have tried to compose an image displaying apparatus by using a multi-electron beam source in which many surface conduction electron-emitting devices are arranged two-dimensionally and the arranged surface conduction electron-emitting devices are wired in a passive matrix as shown in FIG. 11. In FIG. 11, a reference numeral 4001 designates a surface conduction electron-emitting device shown mimetically; a reference numeral 4002 designates a piece of wiring in a row direction; and a reference numeral 4003 designates a piece of wiring in a column direction. Incidentally, although a six by six matrix is shown in FIG. 11 on account of the convenience of description, the scale of the matrix is not limited to the six by six one, and devices necessary for displaying a desired image can be arranged.
FIG. 12 shows the structure of a cathode-ray tube using the multi-electron beam source. The structure comprises an outer housing bottom 4005 including a multi-electron beam source 4004, an outer housing frame 4007, and a face plate 4006 including a phosphor layer 4008 and a metal-backing 4009. Moreover, the phosphor layer 4008 on the face plate 4006 includes phosphor thereby excited by an electron beam to emit light, and a black matrix for suppressing the reflection of outer light to prevent color mixture in the phosphor. A high electric potential Va is applied to the phosphor layer 4008 and the metal-backing 4009 through a high voltage terminal 4011, and the phosphor layer 4008 and the metal-backing 4009 constitutes an anode.
For the outputting of a desired electron beam from the multi-electron beam source 4004 in which surface conduction electron-emitting devices 4001 are wired in a passive matrix, appropriate electric signals are applied to the pieces of wiring 4002 in row directions and the pieces of wiring 4003 in column directions of the multi-electron beam source 4004. For example, for the drive of the surface conduction electron-emitting devices 4001 in an arbitrary row of the matrix, a selection potential Vs is applied to the wiring 4002 in the row direction to be selected, and at the same time a nonselection potential Vns is applied to the wiring 4002 in the row directions not to be selected. Synchronously to this, a drive potential Ve for outputting electron beams is applied to the pieces of the wiring 4003 in the column directions.
By this method, the voltages Ve and Vs are applied to the surface conduction electron-emitting devices 4001 of the rows to be selected, and the voltages Ve and Vns are applied to the surface conduction electron-emitting devices 4001 of the rows not to be selected. By the settings of the voltages Ve, Vs and Vns to be appropriate potentials, electron beams having desired strength can be outputted only from the surface conduction electron-emitting devices 4001 of the rows to be selected. And, when drive potentials Ve having different strength from each other are applied to each of the wiring 4003 in the column directions, electron beams having different strength are outputted from each surface conduction electron-emitting devices 4001 in the row to be selected. Moreover, because the response speed of the surface conduction electron-emitting devices 4001 is high, the length of time during which electron beams are outputted can also be changed by the change of the length of time during which the drive potential Ve is applied.
By the application of such electric potentials, the electron beams outputted from the multi-electron beam source 4004 irradiate the metal-backing 4009, which the high electric potential Va is applied to, and excite the phosphor, or the target, to make the phosphor emit light. Moreover, in the image displaying apparatus, the high electric potential Va (sometimes referred to as an xe2x80x9caccelerating potentialxe2x80x9d or an xe2x80x9canode potentialxe2x80x9d) is applied to the metal-backing 4009 to generate an electric field between the outer housing bottom 4005 (sometimes referred to as a xe2x80x9crear platexe2x80x9d) and the face plate 4006. Thereby, electrons emitted from the multi-electron beam source 4004 are accelerated and excite the phosphor to emit light. Consequently, an image is formed.
Now, because the brightness of an image displaying apparatus depends on an accelerating potential greatly, it is necessary to heighten the accelerating potential for the realization of high brightness. Moreover, because the thickness of an image displaying panel should be thinned for the realization of the thinning of the image displaying apparatus, the distance between the rear plate 4005 and the face plate 4006 should be shorten therefor. Consequently, a considerably high electric field is generated between the rear plate 4005 and the face plate 4006.
Now, in the structure equipped with an anode to which accelerating potential for accelerating an electron is applied, undesirable discharges are sometimes generated between the anode and other members.
The inventors of the present invention planned to dispose a potential regulating electrode capable of suppressing the discharge between the anode and any other member capable of generating a creeping discharge between the anode at a halfway point of a creepage between the anode and the other member.
As a result of the zealous consideration, the present inventors found a fact that the employment of a structure in which a further spacing member is disposed in the structure having the potential regulating electrode would cause the problem of an abnormal discharge owing to the existence of the spacing member.
One object of the invention is to realize a structure capable of suppressing undesirable discharges in a structure including an anode, a potential regulating electrode and a spacing member.
An image displaying apparatus according to the present invention is composed as follows. That is, an image displaying apparatus comprising:
a first plate including at least an electron beam source;
a second plate including an anode to which an electric potential for accelerating an electron beam from the electron beam source is applied, and a potential regulating electrode to which a predetermined electric potential lower than that of the anode is applied, the potential regulating electrode being situated at an outside of the anode; and
a spacing member provided between the first and second plates, the spacing member contacting both of the anode and the potential regulating electrode, the spacing member including an electrode contacting or being disposed close to the potential regulating electrode thereby electrically coupled with the potential regulating electrode.
Moreover, in the aforesaid invention, a configuration in which the spacing member further includes an electrode contacting or being disposed close to the anode thereby electrically coupled with the anode is preferably employed.
Moreover, in each invention mentioned above, a configuration in which the spacing member further includes an electrode contacting or being disposed close to the electrode disposed on the first plate side thereby electrically connected with the electrode can preferably be employed.
As an electrode to be disposed on the first plate side, an electrode to be disposed on the first plate may be employed. As the electrode to be disposed on the first plate, wiring to be disposed on the first plate can be employed. In particular, the wiring supplying a signal for making the electron source emit an electron to an electron-emitting device may be employed.
Moreover, in each invention described above, a configuration to supply the earth potential to the potential regulating electrode or a configuration to supply an electric potential equal to the lowest electric potential among electric potentials supplied to the electron beam source or more may be employed.
Moreover, in each invention described above, a configuration may-preferably be employed where the anode include an image area in which a phosphor emitting light by being irradiated with electrons from the electron beam source; and when an averaged height of a portion of the anode contacting the spacing member on an outside of the image area is indicated by Da, and a surface roughness of the portion is indicated by Ra, and an averaged height of a portion of the potential regulating electrode contacting the spacing member is indicated by Db, and a surface roughness of the portion is indicated by Rb, the averaged heights Da and Db and the surface roughnesses Ra and Rb meet following conditions: |Daxe2x88x92Db|xe2x89xa62Ra, and |Daxe2x88x92Db|xe2x89xa62Rb. Incidentally, the height referred herein means the height of the contacting surface of the anode with the spacing member measured from a common reference surface (hereupon, the surface of the second plate).
Moreover, in each invention described above, a configuration may preferably be employed in which at least an area of the second plate between the anode and the potential regulating electrode has a sheet resistance within a range of 107 (xcexa9/xe2x96xa1) to 1014 (xcexa9/xe2x96xa1).
Moreover, in each invention described above, a configuration may preferably be employed in which a high resistance membrane is formed at least in an area of the second plate between the anode and the potential regulating electrode.
Moreover, in each invention described above, a configuration may preferably be employed in which an area having a sheet resistance within a range of 107 (xcexa9/xe2x96xa1) to 1014 (xcexa9/xe2x96xa1) exists on the spacing member at least between a portion thereof contacting the anode and a portion thereof contacting the potential regulating electrode.
Moreover, in each invention described above, a configuration may preferably be employed in which a high resistance membrane is formed on the spacing member at least between a portion thereof contacting the anode and a portion thereof contacting the potential regulating electrode.
Moreover, in each invention described above, a configuration may preferably be employed in which the spacing member includes an electrode contacting or being disposed close to the anode thereby electrically coupled with the anode and an electrode contacting or being disposed close to the potential regulating electrode thereby electrically connected with the potential regulating electrode; and an area between the electrode contacting or being disposed close to the anode thereby electrically coupled with the anode and the electrode contacting or being disposed close to the potential regulating electrode thereby electrically connected with the potential regulating electrode has a sheet resistance within a range of 107 (xcexa9/xe2x96xa1) to 1014 (xcexa9/xe2x96xa1).
Moreover, in each invention described above, a configuration may preferably be employed in which the spacing member includes an electrode contacting or being disposed close to the anode thereby electrically coupled with the anode, an electrode contacting or being disposed close to the potential regulating electrode thereby electrically connected with the potential regulating electrode and a high resistance membrane contacting or being disposed close to each of the electrode contacting or being disposed close to the anode thereby electrically coupled with the anode and the electrode contacting or being disposed close to the potential regulating electrode thereby electrically connected with the potential regulating electrode thereby electrically connected with them.
Moreover, in each invention described above, a configuration may preferably be employed in which the spacing member includes an electrode contacting or being disposed close to the anode thereby electrically coupled with the anode and an electrode contacting or being disposed close to the potential regulating electrode thereby electrically connected with the potential regulating electrode; and an interval between the electrode contacting or being disposed close to the anode thereby electrically coupled with the anode and the electrode contacting or being disposed close to the potential regulating electrode thereby electrically connected with the potential regulating electrode is substantially the same as an interval between the anode and the potential regulating electrode. Hereupon, xe2x80x9csubstantially the samexe2x80x9d means to be: (the interval between the anode and the potential regulating electrode)xc3x970.8xe2x89xa6(the interval between the electrode contacting or being disposed close to the anode thereby electrically connected with the anode and the electrode contacting or being disposed close to the potential regulating electrode thereby electrically coupled with the potential regulating electrode)xe2x89xa6(the interval between the anode and the potential regulating electrode)xc3x971.2.
Moreover, in each invention described above, a configuration may preferably be employed in which an interval between a projective position of an extreme point on the anode side of the potential regulating electrode to the spacing member and a position of an extreme point on the anode side of an electrode contacting or being disposed close to the potential regulating electrode of the spacing member to be electrically connected with the potential regulating electrode is ten percent or less of an interval between the potential regulating electrode and the anode. When the extreme point contacts the spacing member, the xe2x80x9cprojective position of an extreme point on the anode side of the potential regulating electrode to the spacing memberxe2x80x9d corresponds to the contacting point of the extreme point with the spacing member. That is, by the suppression of the positional shifting between the electrode formed on the spacer and the potential regulating electrode, discharges can preferably be suppressed.
Moreover, in each invention described above, a configuration may preferably be employed in which the spacing member includes an electrode contacting or being disposed close to the anode thereby electrically connected with the anode; and an interval between a projective position of an extreme point on the potential regulating electrode side of the anode to the spacing member and a position of an extreme point on the potential regulating electrode side of the electrode of the spacing member, the electrode contacting or being disposed close to the anode thereby electrically connected with the anode, is ten percent or less of an interval between the potential regulating electrode and the anode. When the extreme point contacts the spacing member, the xe2x80x9cprojective position of an extreme point on the potential regulating electrode side of the anode to the spacing memberxe2x80x9d corresponds to the contacting point of the extreme point with the spacing member.
Moreover, in each invention described above, a configuration may preferably be employed in which at least a part of the second plate and the spacing member contacts between the potential regulating electrode and the anode of the second plate.
Moreover, in each invention described above, a configuration may preferably be employed in which a structure contacting the spacing member is provided in an area between the anode and the potential regulating electrode of the second plate.
In this configuration, it is preferable to set the averaged heights Dc, Da and Db and the surface roughnesses Ra and Rb to meet at least one of following formulae: |Daxe2x88x92Dc|xe2x89xa62Ra, |Dbxe2x88x92Dc|xe2x89xa62Rb, when an averaged height of the structure contacting the spacing member of the second plate is indicated by Dc, and an averaged height of a portion of the anode contacting the spacing member is indicated by Da, and a surface roughness of the portion is indicated by Ra, and an averaged height of a portion of the potential regulating electrode contacting the spacing member is indicated by Db, and a surface roughness of the portion is indicated by Rb.
Moreover, in each configuration described above, it is preferable that the structure contacting the spacing member of the second plate is composed of a high resistance material. Moreover, a configuration can preferably be employed in which a high resistance membrane having a volume resistivity lower than that of the structure is formed on a surface of the structure contacting the spacing member of the second plate.
Moreover, in each invention described above, a configuration may preferably be employed in which the spacing member has a structure for contacting an area between the anode and the potential regulating electrode of the second plate. In this case, a configuration may preferably be employed in which the structure of the spacing member for contacting the area between the anode and the potential regulating electrode of the second plate is a projecting configuration.
Moreover, in each invention described above, a configuration may preferably be employed in which the spacing member includes a high resistance membrane. In this case, it is preferable that a sheet resistance of the high resistance membranes of the spacing member is within a range of 1xc3x97107 (xcexa9/xe2x96xa1) to 1xc3x971014 (xcexa9/xe2x96xa1).
Moreover, in each invention described above, a configuration may preferably be employed in which the electron beam source provided on the first plate is disposed in a matrix. Moreover, it is preferable that the electron beam source is composed of surface conduction electron-emitting devices.